Miniature drum indicator

ABSTRACT

In an electrical meter, the indicator includes a drum driven by a moving-magnet-type meter movement. A helical pattern on the drum moves relative to a flat scale to represent the value of an applied electrical signal.

United States Patent Fleetman (4 1 Jan. 25, 1972 154] MINIATURE DRUMINDICATOR [72] Inventor: Hobart 11. Fleetman, Perkasie, Pa.

[73] Assignee: Electro-Mecha'nica l lnsti'ument C0., l ne,

Perkasic, Pa.

[22] Filed: Mar. 14, 1969 [21] Appl.No.: 807,267

[52] U.S. Cl. ..324/l46, 324/151 R, 340/373 [51] lnt.Cl ..G0lr 1/20,GOlr 1/16 [58] Field oiSearch ..324/l46, 147, 156,151;

[56] References Cited UNITED STATES PATENTS 3,074,060 1/1963 Kadlec..324/146UX 3,376,569 4/1968 Watkins ..340/373 X 3,518,665 6/1970Bristol ..340/373 FORElGN PATENTS OR APPLICATIONS 7,182,342 11/1964Germany ..324/l5l Primary Examiner-Alfred E. Smith At!0rneyWoodcock,Washburn, Kurtz & Mackiewicz [57] ABSTRACT In an electrical meter, theindicator includes a drum driven by a moving-magnet-type meter movement.A helical pattern on the drum moves relative to a flat scale torepresent the value of an applied electrical signal.

3 Claims, 3 Drawing Figures MINIATURE DRUM INDICATOR BACKGROUND OF THEINVENTION This invention relates to electrical meters and moreparticularly to an electrical meter having a drum-type indicator.

There exists a requirement for an electrical meter having a long flatscale and which can be driven from a low level electrical signaL, Inparticular, this need exists for use with tuners of the voltage tunedtype used, for example, in radio and TV sets. In voltage tuners, the aircapacitor used in normal tuners is replaced by a variable resistortogether with a solid-state voltage sensitive capacitor to obtain thedesired tuning. In tuners using variable air capacitors, the mechanicalposition of the tuning knob is a fairly reliable indication of thefrequency to which the tuner is tuned. Hence, tuners of that type merelyprovide a scale used in relation to the tuning knob to indicate thestation tuning.

However, in voltage tuners the position of the tuning knob is notnecessarily a reliable indication of tuning, particularly where standardgrade variable resistors are used. In voltage tuners, there is, however,a voltage available which is a reliable indication of the station towhich it is tuned. It has been proposed to provide a meter-typeindicator which is responsive to this voltage to provide an indicationof station tuning.

Some of the requirements of such a meter are that be relatively simple,low cost and rugged.

The desired display for such a meter can be met by indicators of thedrum type. Such indicators for other purposes are shown in US. Pat. Nos.1,828,053, Kourtzman, and, 2,9l0,036, Lasko, which show drum-typeindicators for speedometers.

Electrical meters with drum-type indicators are shown in the copendingapplication of my coworker, Elbert Kennedy Mackenzie, Ser. No. 807,268,filed Mar. 14, 1969.

SUMMARY OF THE INVENTION In accordance with an important aspect of thepresent invention, there is provided an electrical meter having a drumindicator.

The drum has a helical pattern, or a helical stripe around the peripheryof the drum. When viewed through a slot having the scale associatedtherewith, the rotation of the drum in response to the application of aninput signal gives the effect of an advancing stripe which movesrelative to the scale and provides an indication of the value of theapplied input signal.

Accordingly, it is one object of the present invention to provide aflat, straight scale electric meter with a readout which minimizesparallax.

It is another object of the present invention to provide a meter havinga rugged, simple construction for commercial and industrial service.

It is another object of the present invention to provide a low costmeter having a construction which is suitable for large quantityproduction and for low power consumption in service.

It is another object of the present invention to provide a meter whichcan be easily read by nontechnical users without ambiguity, can be readat a distance and can be read in direct sunlight (an attribute notpresent, for example, in optical projection meters).

It is another object of the present invention to provide an electricalmeter which is compatible with voltage tuning of TV, radios, amplifiers,electronic circuitry and automotive tachometers and which avoidsprecision potentiometer shaft position indication.

It is another object of the present invention to provide an indicatorwhich is suitable for use with a remote tuner of the variable voltagetype.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more detailed descriptionand appended claims.

DESCRIPTION OF THE DRAWINGS FIG. I shows the meter of this inventionpartially in section;

FIG. 2 is a sectional view along the lines 22; and FIG. 3 IS a sectionalview along the lines 3-3.

DESCRIPTION OF A PARTICULAR EMBODIMENT Referring now to the drawings,the meter includes the drum 1. The drum has a pattern thereon dividedinto two colors or shades. The dividing line between the two portions isa helix around the drum. Dividing the periphery of the drum into red andwhite areas provides a particularly distinctive display.

The drum 1 is mounted on an arbor 2 which is joumaled in the frame 3.Mounted on the arbor 2 is the moving magnet armature 4. The armature isdisposed within the electrical coil 5. The coil is electricallyconnected to the terminals 6 and 7. An electrical signal, the magnitudeof which is to be displayed, is applied to the terminals 6 and 7.

In order to set the zero of the meter, a rotatable control magnet 8 isprovided. This coacts with the armature to adjust the zero position ofthe drum.

The drum and meter movement are enclosed within the case 9. The case hasa scale 10 disposed adjacent the viewing slot 11. The scale is protectedby the transparent meter face 12.

In operation, an electrical signal applied to the terminals 6 and 7results in rotation of the drum 1. As the drum rotates, the helicalpattern presents an advancing stripe relative to the scale 10. Theposition of the stripe relative to the scale presents an easily readableindication of the magnitude of the electrical signal.

As previously discussed, this type of meter is easily adapted for usewith a voltage tuner so that the meter provides a good and reliableindication of the frequency to which the tuner is tuned.

While a particular embodiment of the invention has been shown anddiscussed, it will be understood that various modifications may be madewithout departing from the true spirit and scope of the invention. Theappended claims, therefore, are intended to cover any suchmodifications.

What is claimed is:

1. An electrical meter for indicating the value of an electrical signalapplied thereto comprising:

a rotatable drum indicator,

electrical coil means positioned outside said rotatable drum indicator,said electrical signal being applied to said electrical coil means,

a moving magnet armature disposed inside said coil magnetically coupledto said electrical coil means,

a shaft, said drum indicator being mounted on said shaft,

and

bearings externally mounted for support of said drum, said shaft beingrotatably mounted in said bearings, said drum being mechanically coupledfor rotation by said armature to represent the value of said signal inaccordance with the relative rotation of said drum.

2. The meter recited in claim 1 wherein said drum has a two-sectionpattern around the periphery thereof, the dividing line between said twopatterns being a helix, and wherein rotation of said drum advances saidhelix longitudinally of said drum.

3. The meter recited in claim 2 and,

a case having a viewing slot longitudinal of said drum, said helixpresenting an advancing stripe when viewed through said slot as saiddrum rotates, and

a scale disposed in relation to said slot to indicate the magnitude ofsaid electrical signal.

1. An electrical meter for indicating the value of an electrical signalapplied thereto comprising: a rotatable drum indicator, electrical coilmeans positioned outside said rotable drum indicator, said electricalsignal being applied to said electrical coil means, a moving magnetarmature disposed inside said coil magnetically coupled to saidelectrical coil means, a shaft, said drum indicator being mounted onsaid shaft, and bearings externally mounted for support of said drum,said shaft being rotatably mounted in said bearings, said drum beingmechanically coupled for rotation by said armature to represent thevalue of said signal in accordance with the relative rotation of saiddrum.
 2. The meter recited in claim 1 wherein said drum has atwo-section pattern around the periphery thereof, the dividing linebetween said two patterns being a helix, and wherein rotation of saiddrum advances said helix longitudinally of said drum.
 3. The meterrecited in claim 2 and, a case having a viewing slot longitudinal ofsaid drum, said helix presenting an advancing stripe when viewed throughsaid slot as said drum rotates, and a scale disposed in relation to saidslot to indicate the magnitude of said electrical signal.